Optical deflectors for deflecting light are found in a number of different forms and are included, for example in the presentation device described in Swedish Patent 500,061, as a component worn by an observer and used for widening the line presented by a line display. The above patent proposes opto-mechanical deflection by means of rotating or vibrating mirrors, or by means of rotating wedges. Electro-optical deflection is also proposed.
There are a number of demands and objectives in respect to the properties which should be satisfied by a deflection device worn by an observer and suitable for a presentation device according to this patent. The deflector device should have the following properties, among others being:
achromatic, PA1 mechanically simple, low in volume and lightweight, PA1 suitable for mass-production, for example by replica techniques, that is inexpensive, PA1 usable for several applications.
Opto-mechanical solutions have long existed in traditional instrumental optics. For example, use is sometimes made of a so-called optical micrometer. The latter can consist of two optical wedges which are turned towards one another, or a pair of lenses in which the lenses have the same refractive power, but different characteristics. When one lens is shifted sideways relative to the other, the optical beam path is refracted by an angle which is proportional to the movement. The optical systems can be rendered achromatic and generally give small residual errors. Other opto-mechanical deflector solutions involve various types of controlled or rotating mirrors, rotating prisms, etc. These optical systems have undergone extensive development on the basis of IR technology and laser technology. However, the known opto-mechanical solutions, as outlined above, still involve comparatively large and cumbersome mechanics, which are in addition relatively expensive and difficult to manufacture.
In recent times there have been considerable developments in the sector of micromechanics, and these developments have resulted in, among other things, micromechanical mirror matrices for image projection, etc. The production processes used in semiconductor technology are employed in the manufacture of the mirror matrices. The known mirror matrices are unsuitable for use as a deflector device worn by an observer, because the small mirror dimensions give powerful diffraction effects. It has also been proposed to use micro-lens matrices which can be displaced relative to each other. A micro-optical laser scanner based on micro-lens matrices is already known from M. Edward Montamedi, "Miniaturized micro-optical scanners", Optical Engineering, vol. 33, no. 11, November 1994, pages 3616 to 3623. This micro-optical laser scanner involves small dimensions, &lt;1 mm, and there are both diffractive and refractive elements. On account of the diffraction effects which occur with these small dimensions, these micro-lens matrices are also unsuitable for use in the application according to the invention, i.e. to be worn by an observer.
Electro-optical solutions are in most instances based on some form of voltage-controlled crystal optics in combination with polarizers. They generally require high voltages, and this creates a problem. The solutions are often quick to implement, but require a relatively large construction volume.
Acoustic-optical deflectors are based on Bragg effects in acoustically generated gratings. Thus, they are in general greatly limited in chromatic terms, but otherwise have many attractive properties.
A new and promising technique uses so-called liquid crystals. A dynamic phase grating can be generated with high resolution, in principle a hologram. However, this effect is based on the wave characters of light and is therefore limited in wavelength.
In summary the opto-mechanical solutions lead to achromatic deflectors, but they can be cumbersome and difficult to manufacture. The other principles which have been mentioned above make use of the wave nature of light and are therefore limited spectrally or are even completely impossible because of diffraction effects.